Kitab al-Fıraq is an important work belonging Abu Muhammad al-Yemenî. It reflects sectarian perception of Sunni scholars who lived in Yemen in the sixth century AH. But there is not enough information about the author and his work in the sources. But it is known that he has affected some scholars like Saksaki. In addition, influences of political, social and religious structure of Yemen can be seen in Kitab al-Fıraq. Ash'arite, Ashâbu'l-Hadith, Ismaelite, and Zaidiyyah were the most common sects in Yemen at that time. The social life of the region had been shaped by politics behaving sectarian competition. Hence, written books had ideological contents. Sectarian fanaticism was affecting the descriptions made on opponents. For instance, Abu Muhammad has used exclusionary language about dissident sects. In addition, he has selected the marginal views of sects; moreover, presented some opinions by falsifying and sometimes made generalizations. Therefore, modern researchers should be careful while using his book and similar works of Islamic heresiographical literature about problems such as these.